Epilepsy is a disorder of imbalance between neuronal excitation and inhibition. Several genes that are responsible for human epilepsy have been identified, however, most remain unknown due to the underlying complex genetics. Adult "fitful" mice carrying one copy of a novel mutation in the gene encoding Dynamin-1, a large GTPase involved in endocytosis and synaptic membrane recycling in neurons, experience recurrent idiopathic limbic and tonic-clonic seizures. Fitful adolescents with both copies mutated have more severe seizures, in addition to ataxia and neurosensory deficits. Interestingly, Dynamin-1 null mutants, while neurologically impaired, do not show these particular abnormalities. Study of the new fitful mutation therefore provides a unique opportunity to better understand the relationship between normal synaptic function and neurological disease. Preliminary data show that the mutation resides in an alternative exon of Dynamin-1, encoding one of two isoforms, and that it has a dominant negative effect on protein assembly and endocytosis in vitro. Our first aim is to determine in more detail the consequences of normal and mutant isoforms on endocytosis in primary neuronal cells, by introducing wild-type and mutated Dynamin-1 cDNA into Dynamin-1 null primary neurons in culture as well as established neuronal cell lines. Endocytosis and synaptic vesicle recycling will be examined in transfected neuronal cultures as well as proper synaptic protein localization. The second aim is to ask if the fitful mutation has an effect on synapse formation and maturation. Synaptogenesis will be evaluated in transfected primary neuronal cultures and cell lines by quantification and localization of pre- and post-synaptic markers. The fitful mouse is a novel and intriguing model for generalized idiopathic epilepsy, stemming from a gene about which there is already a great deal of understanding but none so far tied directly to epilepsy. Fitful will give us insight to at least one pathway that is likely to be involved in the very complex genetics that underlie idiopathic epilepsies. PUBLIC HEALTH RELEVANCE: As a disorder of "excitability" of the brain, epilepsy is a devastating malfunction of the intricate balance between neuronal excitation and inhibition. Disruption of proper Dynamin-1 mediated endocytosis in neurons results in defective neuronal transmission. Studying how Dynamin-1 functions and contributes to the stability of synapse dynamics will help us to understand how perturbation of endocytosis leads to seizure generation and may provide for novel approaches to future therapies.